Variable condenser



Aug. 18, 1931. SHAPIRO VARIABLE CONDENSER Filed Jan. 9, 1923 gvwemtoz LHAPIRO 35% k1 adieu W1 3i M Patented Aug. 18, 1931 UNITED STATES PATENTOFFICE LAZARUS SHAPIRO, OF BRONX, NEW YORK, ASSIGNOR TO RADIOCORPORATION OF AMERICA, A CORPORATION OF DELAWARE VARIABLE CONDENSERThis invention relates to variable condensers such as are employed inwireless telegraphy and telephony.

As is well known, wireless transmittersand receivers comprise circuitswhich may be tuned to the length of the waves which 1t is desired totransmit or receive. .As is also well known, the tuning of a circuitdepends on the inductive and capacitive efi'ects of the 'circuit. Insuch circuits it is customary to maintain the inductive effectsubstantially constant and to vary the tuning or wave length of thecircuit by regulating the capacity. The capacity effect is obtained bythe use of condensers, and the length of the wave transmitted or thelength of the wave to which a receiver is tuned is usually varied byadjusting certain elements of a condenser relatively to certain otherelements.

,vide a variable condenser, articularly for use in receivers, with meansor adjusting the condenser approximately to the wave length which it isdesired to receive and auxiliary means for effecting minute adjustmentsof the condenser to tune the receiver exactly to the length of theincoming waves. Such condensers have also been provided with scales forindicating the capacity to which the condenser is set by actuation ofthe primary adjusting means. The arrangement of such condensers has,however, generally been such that the reading of the scale has not beenaffected by the auxiliary means for making the minute adjustments, andthat the capacity of the condenser might be varied by operation of theauxiliary adjusting means through a range corresponding to a number ofgraduations on the scale, with the result that yvhen the condenser wasfirst set to the approximate wave length by the primaryadjusting meansand was then adjusted by the auxiliary adjusting means, as nearly as theconstruction of the condenser would permit, to the exact length of theincoming waves, the indicating means no longer showed theprecisecapacity to which the condenser had been set,

It is an object of this invention to provide a variable condenser whichcan be It has heretofore been proposed to proquickly set by primaryadjusting means approximately to the incoming wave length,

and which may then be adjusted by auxiliary adjusting means exactly tothe incoming Wave length with appropriate movement of the indicatingmeans so as to cause such means to invariably show the precise capacityto which the condenser is set, or in other words, assuming that theinductive effect of the receiver is constant, the wave length to whichthe circuit, of which the condenser is a part, is tuned.

It is frequently important in the design of radio receiving sets,particularly for the reception of broadcasted speech or music, to employa condenser occupying a minimum amount of space in proportion to itscapacity. Such a condenser is, for example, of great advantage in theconstruction of a sound reproducing machine, such as that shown in theco-pending ap lication of Alfred N. Goldsmith, Serial 0. 587,067, filedSept. 9, 1922, which comprises a combined phonograph and radio receiverin which the radio receiving apparatus is mounted in the cover of themachine casing. The space available in the cover of such a machine islimited, particularly in its vertical dimensions, and it is accordinglynecessary that the condensers employed in the radio receiving apparatusshall be small, particularly in thickness.

A further object of this invention is to provide a condenser which willaflord maximum capacity in proportion to the amount of space occupied byit.

An important feature of the invention resides in the provision of acondenser, includmore movable plates mounted on a shaft and havingcurved outer. edges, of indicating means connected with the movableplates and meansfor positively engaging the outer edges of the movableplates to effect minute adjustments of said plates relatively to thestationary plates. In the preferred form of the invention, the movableplates are mounted rigidly on a shaft having a dial constructed formanipulation by the hand, and the curved outer edges of the movableplates are toothed for engagement with a gear, so that the approximatesetting of the condenser can be quickly effected by rotation of thedialand the capacity of the condenser can be regulated and the dialsimultaneously rotated by actuation of the gear to adjust the condenserexactly to the wave length, which it is de-' sired to receive, theresult being that the scale on the dial at the point of best receptioninvariably indicates both the exact capacity of the condenser and theprecise length of the incoming wave.

A still further feature of the invention contemplates the provision of acondenser including a shaft having longitudinal ridges thereon andplates mounted on the shaft and having portions cooperating with the rides to maintain the plates and the shaft rigidly together.

Other objects and features of the invention will appear as thedescription proceeds and will be pointed out in the appended claims.

In the drawings, in which like reference numerals indicate like partsthroughout the various views,

Fig. 1 is a view in'elevation of a variable condenser embodying theinvention;

Fig. 2 is a view in horizontal section taken along the line 2-2 of Fig.1;

F i 3 is a view showing the manner in whic the plates of the condenserare assembled upon the shaft; and

Fig. 4 is a sectional detail taken along the line 44 of Fig. 3.

The frame of the illustrated device comprises a circular top 2 andbottom 4 composed of insulating material and connected by upright rods6, 8 and 10, Fig. 2. Stationarily mounted on the frame is a set ofplates 12 of enerally semi-circular form provided with lots or notches14 to receive the rods. The plates .12 are supported and spaced fromeach other by suitable washers 16 sleeved upon the rods, and arranged ininterdigital relation with the stationary plates 12 is a set of movableplates 18. As shown, the plates 18 are of somewhat smaller size than theplates 12, but are also generally of semi-circular form. The plates 18are carried by a shaft 20 journaled in the top 2 and bottom 4 of theframe of the device.

The movable lates 18 are connected rigidly to' the shaf t 20 forrotation therewith in both directions. The preferred means for thusconnecting the plates 18 and the shaft is shown in Figs. 3 and 4 andcomprises ridges 22 extending longitudinally of the shaft 20 andprovided with sharp outer edges 24 which will hereinafter, for the sakeof convenience, be referred .to as knife ed es. In the assembly of theplates 18 and s aft 20, the plates may be driven upon the shaft by asuitable tool indicated by dotted lines 25 in Fig. 3, thereby causin theknife edges of the ridges 22 to enter t e material of the plates 18around the central openings 26 therein, so asto cause portions 27 of theplates 18 in the assembled construction to interlock with the ridges 22of the shaft. The interlockin of the portions 27 of the plates 18 withtie ridges 22 of the shaft 20 causes the plates 18 to be rigidly joinedto the shaft 20, so as to move therewith without lost motion, even afterextended use of the condenser. Preferably, and as indicated in Fig. 4,the openings 26 in the plates 18 are made of slightly greater diameterthan that of the shaft 20 exclusive of the ridges 22, thereby enablingthe plates 18 to be readily driven upon the shaft without warping them.The plates 18 are spaced from each other by suitable washers 28, Fig. 2,on the shaft 20.

Mounted on the upper end of the shaft 20 is a dial 29 provided with aperipheral scale 30, and preferably constructed so that it maybe'readily manipulated by the hand. To this end, the dial may, forexample, be provided with a knob 32 having its periphery knurled asindicated at 33. With this construction, it is apparent that uponrotation of the knob 32 or plates 18 in either direction, such rotationwill be communicated to the entire assembly consisting of the set ofplates 18, dial 29 and knob 32. In other words, it will be clear notonly that the set of movable plates 18 may be adjusted relatively to thestationary plates 12 by rotation of the dial 29 in either direction butalso that rotary movement of the set of plates 18 however effected, willbe communicated to the dial 29 and scale 30;

mg means for rotatin the movable p ates 18 relatively to the stationaryplates 12. In the use of the condenser, such means may conveniently beemployed for quickly setting the condenser so as to tune the receivercontaining the condenser approximatel to the wave length of the signalswhich it is desired to receive. It is found, however,

The knob 32 constitutes primary adjust-.

to positively engage, and operate the plates 18, and as shown comprisesgear teeth 34: formed on the outer curved edges of each of the plates 18and meshing with a gear 36 composed of insulatin material and carried bya shaft or spin le 38 journaled in the top 2 of the condenser frame. Inorder to facilitate rotation of the gear 36, the spindle 38 is preferablprovided" adjacent to the dial 29 with a nob 40 or the like. Thecondenser may be provided in a known manner with means for makingelectrical connections to the set of stationary plates 12 and the set ofmovable plates 18.

It will be apparent from the foregoing that very minute adjustments ofthe set of movable plates 18 relative to the set'of stationary p ates 12may be effected by operation of the gear 36, and that movement of theplates 18 by the gear 36 produce simultaneous movements of the dial 29and scale 30 so as to cause the dial to indicate the true capacity ofthe condenser, both when the condenser is set solel by movement of theknob 32 and when t e settin of the condenser involves the use of t eperipheral gear 36. It will also be understood that, assuming that theinductive effect of a circuit in which the condenser is to be em-'ployed, is maintained constant, the scale 30 of the dial 29 may becalibrated in wave lengths so that at the point of best reception, thescale 30 will indicate directly the length of the incoming wave.

It is recognized that the broad principles of the invention may beembodied in a condenser in which one or other number less than all ofthe movable plates 18 are engaged at their outer edges with the gear 36or other operating means separate from the shaft 20. It is preferred,however, that the gear 36 be caused to operatively engage Elsieperipheries of all of the movable plates In the use of condensers, asheretofore constructed, it frequentl occurs that the joints between themova le plates and the shaft on which they are mounted become loosened,so that lost motion is developed between some or all of the plates andthe shaft. The plates, consequently, become displaced to a greater orless degree with re- Epect to each other and to the shaft. Suchisplacement obviously affects the capacity of the condenser so that theindicating means which is commonly operated from the shaft of thecondenser no longer shows its real capacity. -As :heretofore pointedout, the

occurrence of such lost motion between the 1 movable plates and theshaft is largely revented by the special connecting means i ustrated inthe accompanying drawing. If however, 11 tween a o the plates 18 and theshaft 20, tliegar 36, in the event that it is operatively described forefi'ectin looseness should develop b eefl'ect rotation of the gear 36,and the gear 36 will in turn rotate any plate, which may be loose on theshaft 20, to exactly the same extent as that to which thefirst-mentioned plates are rotated. From these considerations, it willbe seen that the gear 36 not only constitutes auxiliary adjusting meansfor effecting minute relative adjustments of the sets of-movable andstationary plates, but that such gear also constitutes means forpositively maintaining the movable plates 18 in proper relation to eachother and to the shaft 20, so that the capacity of the condenser cannotbe changed by displacement of the plates relatively to each other or theshaft, thereby eliminating all possibility of errors arising from suchdisplacement in the indicated capacity of the condenser.

The provision of the means here-inbefore minute relative adjustments ofthe sets 0 movable and stationary' plates enables a condenser to be madeof small dimensions, particularly in regard to height or thickness, inproportion to its capacity because it avoids the necessit of theprovision of driving gears or the li e separate from the movable platesfor operating them and because it simplifies generally the constructionof the condenser, diminishing the number of parts required andconsequently reducing the space requirements of the parts. i

Although the condenser is herein described as being of the typecomprising generally semi-circular plates, certain of which are carried.by a shaft, it is recognized that the stationary plates of the condenseris intended to embrace a single plate as well as a plural- 't of plates,in the event that the context of a claim is consistent with theinterpretation of the term as including a single plate only.

Having fully described my invention what I claim is:

1. A variable condenser comprising a shaft having ridges extendinglongitudinally thereof and a plate inounted on the shaft, said ridgesbeing embedded in a portion of the plate to cause the plate to be heldrigidly upon the shaft for rotary movement therewith without lostmotion.

2. A variable condenser comprisin a shaft provided with integral ridgesexten ing longitudinally of the shaft and having sharp outer edges, andplates mounted upon the shaft, the ridges being embedded in a portion ofeach plate to hold the plates and shaft rigidly together.

3. A variableeondenser comprising stationary plates, a rotatable shafthaving serrations formed thereon, and movable lates mounted on saidshaft, said serrations ing embedded in a portion of each plate, wherebysaid movable plates may be moved relatively to said fixed plates,without backlash between the said movable plates and the rotatableshaft.

4. A variable condenser comprising a shaft having longitudinal ridges, aseries of lates mounted upon said shaft, said ridges ing embedded in aportion of each plate in order to provide a firm union between saidplates and shaft, means carried by said shaft to rotate the plates, andseparate means spaced from said first mentioned means .to provide aVernier adjustment of said plates.

5. In a condenser, a rotatable shaft rovided with a plurality ofsharp-edged, we geshaped projections, one or more rotor plates mountedon said shaft, said projections being embedded in a portion of eachplate 6. In a condenser, a shaft provided with a plurality ofsharp-edged projections, one or more plates mounted on said shaft, saidprojections being embedded in a portion of each late. I) 7. In acondenser, a rotatable shaft provided with a plurality of grippingmembers, one or more rotor plates mounted on said shaft, said grippingmembers being embedded in a portion of each plate.

LAZARUS SHAPIRO.

